org chem applications

polyethene

addition polymer

plastic bottles, toys, plastic bags, film wrap

PVC

aka polychloroethene, addition polymer

plastic pipes, artificial leather, wire insulation

PTFE

addition polymer

coating for non-stick pans

polypropene

addition polymer

lab equipment, automobile parts

polystyrene

addition polymer

styrofoam

starch/glucose

• enzymes act as biological catalysts

• condensation polymerisation of glucose (monomer) into starch (polyamide) + water

• reverse: hydrolysis, break down polymer into monomers using water

polyethylene terephthalate (PET)

low permeability to CO2, used in bottling of canned drinks

kevlar

polyamide with benzene ring

spider silk (naturally occuring)

polypeptide

polyamide formed from amino acids

renewable energy sources

naturally replenished, will not run out

• biofuels

• solar energy

• wind

• hydroelectric

• tidal

• geothermal

• nuclear fusion

non-renewable energy sources

finite, will run out

• fossil fuels (coal oil natural gas)

• nuclear fission

• electrochemical cells: redox reaction generates electricity

formation of fossil fuels

• plant matter contains CHO from photosynthesis (glucose) + contains N and S because of protein. plants consumed by animals.

• anaerobic decay of biological material: absence of oxygen, compressed and acted on by bacteria

coal

• formed from remains of plants that were buried → partial decomposition in absence of oxygen, high temperature and pressure

• mostly carbon, also HONS

• % of C increases, burn more cleanly and releases more heat on combustion

advantages

• supply should last 100s of years

• distributed throughout the world

• can be converted to synthetic gaseous/liquid fuels

• can be converted to feedstock for the petrochemical industry

• more concentrated source of energy

• relatively cheap to produce

disadvantages

• produces greenhouse gases when burned → climate change

• acid rain + particulates

• less easy to transport

• mining is dirty and dangerous

crude oil (petroleum)

• formed from remains of plankton that sank to bottom of sea and buried → absence of oxygen, high pressure, moderate heat (60-170C)

• is a mixture of hydrocarbons, also ONS

advantages

• easier to extract and transport than coal

• convenient for internal combustion engine

• source of variety of chemicals for the petrochemical industry

disadvantages

• produces greenhouse gases when burned → climate change

• acid rain

• supply could run out in decades

• extraction + transportation in tankers → env issues

• few countries have reserves

natural gas

• formed from remains of plankton that sank to bottom of sea and buried → absence of oxygen, high pressure, moderate heat (60-170C)

• mostly CH4 and light hydrocarbons and HS

advantages

• cleanest fossil fuel due to low % of C

• easiest to extract and transport (using pipes)

• releases highest amount of energy per mass of fuel

• produces least CO2 per J of energy

• cheap to produce: is a byproduct of coal/oil production

disadvantages

• produces greenhouse gases when burned → climate change

• acid rain

• supply could last less than 100 years

• few countries have reserves

• risk of explosions due to leaks

• most difficult to store because it is a gas: need store under pressure or cool to liquefy it

ways of comparing fossil fuels

1. vol of fuel per mass of fuel

• no. of mol x 22.7 divided by mass = __dm³g^-1

• only if at STP

2. mol/vol of CO2 produced per J

• divide by 1000

• lowest = (natural gas)

3. mass of CO2 produced per mass of fuel

• mol x 44.01 = mass of CO2

  mass of CO2/Mr of fuel = __g

4. carbon footprint

• mass of fuel = density x volume

• no. of mol of fuel = mass/Mr

• mol ratio to find no. of mol of CO2 produced

• mass of CO2 = no. of mol x 44.01 = __g

how could samples be distinguished by combustion?

calculate % of C for each sample. sample with higher % of C has higher tendency for incomplete combustion, will produce more soot when burnt.

greenhouse effect

• initial: some IR reflected back into space, some reach earth’s surface, some absorbed by greenhouse gases then re-radiated back to earth

• earth’s surface emits IR radiation, absorbed by molecules of greenhouse gases → promote to higher energy levels, vibrate more → as move down to ground state, energy given out in all directions → some IR radiation radiated back to earth

  • recall IR spec: only for asymmetric stretch and symmetric bend since there is change in dipole moment

  • water vapour has greatest greenhouse effect: natural frequency corresponds with IR → resonance

  • carbon dioxide has greatest influence on global warming: even though doesn’t absorb much IR radiation, produced in greater amounts

• net effect: higher % of solar energy is trapped in atmosphere → higher average global temperatures

• impact: crop yields decrease, biodistribution (due to desertification and loss of cold-water habitats), rising sea levels (due to melting of ice caps)

biofuels

• plants have CHO because of photosynthesis producing glucose → plant material transformed into fuel

advantages

• renewable source of energy

• can be produced locally, no need expensive oil imports

• can be produced from waste materials

ethanol as biofuel

formed from fermentation of glucose

• C6H12O6 (aq) → 2C5H5OH (aq) + 2CO2 (g)

• conditions: ethanol, yeast catalyst, 37C, absence of oxygen (prevent oxidation of ethanol)

• produces mixture of water, aldehydes, other alcohols and around 8% ethanol, need distillation to concentrate % of ethanol

  • methanol poisoning

  • max concentration 15% ethanol since higher concentration will poison the yeast

• exothermic reaction, need control temperature otherwise will denature enzymes and kill yeast

advantages

• lower greenhouse emissions: produces CO2 but the C in ethanol came from atmosphere (absorbed by plants), so theoretically ‘carbon neutral’

• renewable, produced locally

disadvantages

• lower specific energy than gasoline, need larger volume for same amount of energy

• absorbs moisture from atm, damages engine

• production of ethanol is energy intensive (distillation)

• food vs fuel, price of food increases

biodiesel

formed from transesterification of vegetable oils

• 3 fatty acids (carboxylic acid) + glycerol (triol) → vegetable oils (triglyceride, 3 ester linkages)

• methanol react with vegetable oil → fatty acid ester link to methanol

• condition: strong base catalyst

• reversible reaction, so excess methanol added to shift POE to right

advantages

• biodegradable, less env impact from spillage

• no S, no SO2

• better lubricant than petrodiesel (reduce engine wear)

• theoretically carbon neutral

disadvantages

• higher NOx emissions

• more expensive than petrodiesel

• lower specific energy than petrodiesel, need larger volume for same amount of energy

• production is energy intensive

• food vs fuel, price of food increases

• loss of biodiversity for palm oil plantations

useful chemical property of addition polymers

not biodegradable because they are made of long, stable chains of carbon-carbon bonds ie chemically unreactive